1. Field of the Invention
This invention relates to the sewing machine art, and more particularly to a sewing machine of the type employing a four-motion drop feed mechanism working in opposition to a spring biased presser device. This invention is directed to a solution of the problem of minimizing undesirable lateral drift of work fabrics under the influence of a feed mechanism of the above character. This invention provides a novel presser foot construction which not only virtually eliminates one major cause of feed drift, but does so without sacrificing the versatility of the presser foot; and, in addition, significantly improves the stitch forming characteristics of the sewing machine.
2. Description of the Prior Art
It has long been recognized that the action of the work feed dog may contribute to feed drift and prior patents such as U.S. Pat. No. 3,527,183, Sep. 8, 1979, discuss this factor and teach means for constraining the feed dog to move in a path parallel to the intended line of feed to minimize feed drift from this cause. I am unaware of any prior teaching that the presser device might constitute a contributing factor to feed drift during the return stroke of the feed dog nor am I aware of any teaching of presser foot configurations which would alleviate this source of feed drift. Known presser foot sole plate configurations which include slots, ridges and the like as in U.S. Pat. No. 177,296, May 9, 1976, are provided in order to accommodate work piece protrusions such as stay strips, zipper fasteners, welts and the like, or as in U.S. Pat. No. 2,694,993, Nov. 23, 1954, are provided in order to lessen adhesion to certain types of work fabric. None of these known presser constructions exhibit the relationship to the throat plate as taught by this invention, and thus, none teaches the consequent advantageous beneficial effect minimizing feed drift as well as improving stitch forming characteristics of the sewing machine.